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(i r i i) e 

FOR USING DAVIS' NEW 




fjwjpplifail and Mrottiraikal 

APPA RAT US. 

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DAVIS & WOODS, 

1*0 9MITHFISLD STREET, PITTSBURGH, I'A. 



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JOHN VBBOOa, \... IM I. ill. i-i > lU l H, Pittsliiir K h. Pa. 

\\ . Ml<<»\\ \ a. < <>.. N.i. 17 Park Pin.. . \. » \ nrk. 

.1. \. IHXfiUIFT*. «<>.. \ ... »» \i«li »!.. IMiil.xl, lpliln. Pa, 

Dr. K. .1. TOOK. Knrl 1ln.li-.iii, Iowa, 

.1. ». UUOTSOR8, X.iii,.. Ohio. 

SY1MJEI -"'II I I i . LnvniniMlli, Knii.nv 

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■ HOM I.IItKRAL 
rt, 96 Foarth Arenne, Pittsburgh. 




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«SM0T WITHSTANDING a very brief period has elapsed 
since the Lunatelltjs and Heliotellus were brought before 
the public, and but little effort made to sell them, they are, 
through their own intrinsic merit, finding their way into the 
best Academies, Seminaries and Public Schools of our Country. 
The Public Schools of Boston, Philadelphia, Pittsburgh, Alle- 
gheny, and those of many other Cities and Towns, East and 
West, are using them with much profit in their Primary, as well 
as in their Advanced Classes; also, many of the best High 
Schools, Academies, Seminaries and Colleges have adopted them 
as a permanent and almost indispensable piece of School Apparatus. 
All Teachers and Educators, and every person interested in Ed- 
ucation are especially invited to examine toith care the accuracy 
of these Instruments, and their adaptation for Educational Pur- 
poses. 



Entered according to Act of Congress in the year 1870, b 

JOHN DAVIS, 

In the Office of the Librarian of Congress at Washington. 



|nUJ^ATELLU£ OF} ]4eLIOTELLU£ 



SHOULD BE US EVERY SCHOOL AND FAMILY. 



1. On account of their accuracy in giving just conceptions of j! 
the fundamental principles of Science. 

2. On account of their accuracy in illustrating the grand I; 
mechanism of the Solar System. 

3. On account of their accuracy in illustrating the mutual re- il- 
lations of Geography and Astronomy. 

4. On account of the natural causes and great variety of natu- jj 
ral phenomena which they illustrate. 

5. On account of their illustrating phenomena which cannot jj 
he learned from Maps and Charts. 

6. On account of their illustrating many natural causes and jj 
phenomena which all other Apparatus fails to illustrate. 

7. On account of the ease with which knowledge is imparted |j 
l>y their use, 

v . On account of the ea-e with which knowledge is acquired jl 
by thi'ir use. 

9. On account of the lasting impressions which their move- 
ments make upon the mind. 

10. On account of their practical adaptation to the Library : 
School-room and purposes for which they are designed. 

11. On account of the vast amount of labor and time they j! 
save both Teacher and Pupil. 

12. On account of the satisfaction enjoyed by both Teacher and jj 
Pupil in imparting and receiving instruction. 



=8 



GUIDE FOR USIXG DAVIS' 




Kg. 3,-Iarge Lcnatell 



I EOGRAPHICAL AND ASTRONOMICAL APPARATUS. 



ft 



fui^TEUUS Ap IeLIOTELIUS. 



These [nstrumente, on account of their novelty of form and accu- 

'. were recently patented in the United States, 

Russia, Prance, England, and other countries of Europe. The 

Lunatellus is the Tellurian in a new form, and so improved as to 
illustrate the Astronomical phenomena of the Sun, Earth and Moon 
in their natural order, with the Geography of the Earth always in 
its proper relation to them. The Heliotellus. See next Cut. 

sit N*. 

The Sun is represented by a globe eight inches in diameter, and 
is attached by one of the poles to a rod that connects with the 
gearing. 

EA.RTH. 
The Earth is represented by a globe five inches in diameter — is 
pivoted by the North Pole to the gearing, and is covered with a 
aphical Map. This globe can be detached in a moment, 
from the gearing and placed on a stand for separate use. 

^rooisr. 

The Mood i- represented by a -mailer globe relative in size to 
that of the R\rth, and is carried by a wire which passes through 
its poles and is attached to the gearing. 

aE^LRiTsra. 

The Lunatellus is operated entirely by metallic gearing, part of 
which is inside the case and part at the outer end of the arm that 
carries the Earth and Moon. The large wheel at the outer end of 
the arm that carries the Earth, to which is attached a disk slightly 
inclined, causes the Moon to move in an elliptical orbit, and also to 
he plane of the Ecliptic north and south at an angle of about 
also, her nodes to retrograde a degree and a fraction 
every lunation, thereby causing the Moon to complete her cycle in 
proper time, while the earth is making eighteen revolutions and a 
fraction around the Sun. 



4 GUIDE FOE USING DAVIS' 

ZODIAC. 

A Zodiac thirty inches in circumference containing the twelve 
signs, and-the months in the year corresponding with them is per- 
manently attached to the case. 

MOTION. 

The Lunatellus is put in motion by means of a crank which 
connects in the back part of the case with the gearing. 

convenience. 

This Instrument is always ready for use ; weighs only a few 
pounds ; occupies but little space, and is put in motion with a -few 
ounces of pressure on the crank. 

DURABILITY. 

With proper care this Instrument will last a lifetime, as it is 
composed wholly of metal, except the Maps, and every part free 
from strain or undue pressure. 

UTILITY. 

Geography is so plainly illustrated, and the varied phenomena 
of the Sun, Earth and Moon are expressed with such precision and 
accuracy by the Lunatellus, that more can be learned, even by 
youth, in a few lesson?, than can be learned in months without it, 
hence its necessity in every Family and School. 

INDICATOE. 

The Indicator is seperate from the Instrument, and circular in 
form, with a hole in the centre sufficiently large to admit the globe 
that represents the Earth. 

J)U PLICATE. 

An exact duplicate of any part of the Lunatellus or Heliotellus 
can be obtained by applying to any of the Agents, Proprietors or 
Patentee. 



•:::<S 



lUXiCIJAl'lIh AI. AND ASTRONOMICAL AIT'A I! ATI'S. 



'QEOQF(APHY y\JND ^3TR0jS0MICAL pHEpiOMEN/ 
Illustrated by Davis' Apparatus, 



ILLUSTRATION 1. 
Motions of the Sun, Earth and Moon, and direction of their 
motions. 

ILLUSTRATION 2. 

HI plane of the Ecliptic and its relation to the plane of the 
Equator. 

ILLUSTRATION 3. 

Inclination of the Earth's Axis, and its Parallelism. 

ILLUSTRATION 4. 
Cause of Day and Night. 

ILLUSTRATION 5. 
Day and Night equal, and cause. 

ILLUSTRATION 0. 
3 Days and Short Nights in the Northern Hemisphere. 
ILLUSTRATION 7. 
Long Days and Short Nights in the Southern Hemisphere. 
ILLUSTRATION 8. 
Months Day at the North Pole, and Six Months Night at 
the South Pole, and vice versa. 

ILLUSTRATION 0. 
Cause of the inequality in length of Days and Nights. 

ILLUSTRATION 10. 
Change of Seasons, and Cause. 

ILLUSTRATION 11. 
Cause of the Zones and their width. 



6 GVIDE FOR USING DAVIS' 



ILLUSTRATION 12. 
"Winter in the Northern Hemisphere when the Earth is nearest, 
and Summer when the Earth is farthest from the Sun. 

ILLUSTRATION 13. 
The Sun rising North of the East Point, and setting North of 
the West Point, in Summer, and rising South of the East Point, 
and setting South of the West Point, in Winter. 
ILLUSTRATION 14. 
Cause of the Sun rising earlier to places East of us. 

ILLUSTRATION 15: 
Cause of the apparent'motion of the Sun, Moon and Stars from 

East to West. f 

ILLUSTRATION 16. 

Declination of the Sun, or his apparent motion North and South. 

ILLUSTRATION IT. 
Relative position of the Earth to the Sun at any given period of 
the vear. 

ILLUSTRATION 18. 

The Sun and Earth always in opposite signs of the Zodiac. 

ILLUSTRATION 19. 
Ellipticity of the Earth's Orbit. 

ILLUSTRATION 20. 
Inequality of Siderial and Solar Days, and cause. 

ILLUSTRATION 21. 
Spring and Neap Tides. 

ILLUSTRATION 22. 
The effects of Solar and Lunar Declination on the Tides. 

ILLUSTRATION 28. 
Cause of Constant and Periodic Winds, Trade Winds, Mon- 
soons, &c. 

ILLUSTRATION 24. 

The Moon always presents the same side to the Earth. 

ILLUSTRATION 25. 
Length of Lunar Days and Nights. 



GB0GBAPHEGA1 ANl> astkonom i< Al. APPARATUS. 7 

ILLUSTRATION 20. 
Conjunction, Quadrature, Opposition and Phases of the Moou. 

ILLUSTRATION 87. 
Ellipticity of the Moon's Orbit and its relation to the plane of 

the Ecliptic. 

ILLUSTRATION 88. 

Retrogression of the Moon's Nodes. 

ILLUSTRATION 29. 

Sy nodical and Siderial Revolutions ot' the Moon. 

ILLUSTRATION 30. 
Solar and Lunar Eclips 

ILLUSTRATION 31. 
Why Solar and Lunar Eclipses do not occurevery Revolution of 

the Moon. 

ILLUSTRATION 32. 

Altitude of the Full Moon North and New Moon South in 

Winter. 

ILLUSTRATION 33. 

Altitude of the Full Moon South and New Moon North in 
Summer. 

ILLUSTRATION 34 

The Moon's first quarter low and third quarter high when the 
: Earth i- at the Autumnal Equinox. 

ILLUSTRATION 35. 

The Moon's tirst quarter high and the third quarter low when 
| the Earth is at the Vernal Equinox. 

ILLUSTRATION 86. 
The Moon's Librations. 

ILLUSTRATION 37. 
Zenith and Nadir. 

ILLUSTRATION - 

The Sensible and Rational Horizon. 

ILLUSTRATION 30. 
Verticle Circles, Prime Verdde and Colures. 



8 GUIDE FOR USING DAVIS' 

ILLUSTRATION 40. 
Circles of Perpetual Apparition and Occultation. 

ILLUSTRATION 41. 
The Sun's Zenith, Distance, Altitude and Declination for Lati- j'j 
tude 40 degrees North or South when the Earth is at the Vernal i ; 
or Autumnal Equinox. 

ILLUSTRATION 42. 
The Sun's Zenith, Distance, Altitude and Declination for Lati- \\ 
tude 40 degrees North when the Earth is at the Summer Solstice, jj 

ILLUSTRATION 43. 
The Sun's Zenith, Distance, Altitude and Declination for Lati- I! 
tude 40 degrees North when the Earth is at the Winter Solstice. N 

ILLUSTRATION 44. H 

A Right, Oblique, and Parallel Sphere. 

ILLUSTRATION 45. 
The Azimuth and Amplitude of a Heavenly Body, on, or above i I 
the Horizon. I; 



^JVIercury. 



ILLUSTRATION 1. 
Yearly and Daily Revolutions of Mercury. 

ILLUSTRATION 2. 
Mercury's Axis perpendicular to the plane of its orbit, also its 

parallelism. 

ILLUSTRATION 3. 

Mercury's Days and Nights equal. 

ILLUSTRATION 4. 
No change of Season on Mercury. 

ILLUSTRATION 5. 
Inferior and Superior Conjunctions of Mercury. 



GEOORAl'niCAL AND ASTRONOMICAL APPARATUS. 9 

ILLUSTRATION 8. 

Mercury's Stationary Points. 

ir.l.rsTUATInN 7. 
\\ liy Mercury i< not visible at interior and superior conjunc- 



tions. 

Phases of Mercurv. 



ILLUSTRATION 8. 



Ye j^ u p. 

ILLUSTRATION 1. 
Yearly and Daily Revolutions of Venus. 

ILLUSTRATION 2. 
The inclination of the axis of Venus, its parallelism and the 
plane of her orbit. 

ILLUSTRATION 3. 

Declination of the Sun on Venus. 

ILLUSTRATION 4 
Eight Seasons of Venus at her Equator and Four at her Poles. 

ILLUSTRATION 5. 
Venus the Morning and Evening Star. 

ILLUSTRATION 6. 
Synodic Period of Venus. 

ILLUSTRATION 7. 

Phases of Venus. 

ILLUSTRATION 8. 

Transits of Mercury and Venus. 

ILLUSTRATION 9. 

Occultation of Venus. 



=»■ 



a- 



10 GUIDE I OB USING DAVIS' 



Explanation? and ^ema^k?. 



I. The terms dowv and up are merely relative, meaning towards 
or from the centre of the Earth. If two persons are on opposite 
sides of the Earth, the direction which is down to one is up to the 
other. 

The terms top, under, above, below, &c, when applied, in illus- 
trating, to the globular bodies of the Apparatus, have the same 
meaning that we attach to them when applied to other bodies 
around us. 

II. The terms East and West are relative, for by pointing east- 
ward for twenty-four hours we point to every star on the same par- 
allel, since the earth makes one revolution on her axis in twenty- 
four hours. 

The East and West points are where the sun rises and sets when 
the earth is at either Equinox. 

III. The Natural Zodiac is an imaginary belt 16° in width, ex- 
tending around the heavens east and west. It is divided into twelve 
equal parts called signs. Each sign contains a conspicuous group 
of stars, and these groups are called constellations. Each constel- 
lation was named early in the history of Astronomy, and each 
sign received the same name that the constellation had at that 
time. The plane of the Ecliptic divides the Zodiac into two equal 
parts, 8° being on each side north and south. 

IV. The signs and constellations of the same name in the Nat- 
ural Zodiac, coincided about 2,200 years ago. Since that time the 
first point of the sign Aries (the Earn) has moved westward about 
31° with the Equinox, with which it has alwa} r s coincided. Now 
the first point of the sign Aries, and the first point of the constel- 
lation Pisces (the Fishes), pretty nearly coincide, and the first 
points of the sign Taurus (the Bull) and constellation Aries, &c. 






GECXiRAl'HIfAI \M> A8TBONOMICAI APPARATUS. 



11 



V. The Equinoctial and Solstioial points, OB marked on the Zo- 
diac of the Lunatellus and Heliotcllus, are not named as they are 
generally, from the apparent position of the snn in the Ecliptic at 
different seasons of the year, hut from the position of the Earth in 
her orbit at different period-. For the sake of convenience, the 
Zodiac of the Instruments is made small ami attached to the front 
part of the ease. 

VI. To give the Lunatellus a favorable position, place the back 
towards the north, and for latitude 40° north, if it is desired to 
have the planes of the earth's Equator and Ecliptic in the Instru- 
ment parallel with those in nature, lean the top of the Instrument 
forward about 16 1- °. 

VII. It will not injure the Instrument to turn the crank in 
either direction, but by turuing it from left to right the Sun, Earth 
and Moon will have their natural direction through the signs of 
tin- Zodiac 

VIII. The Sun in the heavens always enlightens the half of each 
body in the solar system next himself; consequently, that half of 
the Earth and Moon next himself is always enlightened. In illustra- 
ting with this Instrument we will regard the Sun AS luminous, 
and always shedding his rays on that half of the earth and moon 
next himself. "Where the light of day and darkness meet around 
each of these bodies, is called the CIRCLE of illumination*. 

IX. In the following illustrations the globular bodies of the 
Apparatus receive the natural names of Sun, Mercury, Venus, 
Earth, and Moon, and it is presumed that the learner is situated 
on the body that represents the Earth, which is called Earth. 



12 GUIDE FOR USING DAVIS' 



Ipgraphg and j^tyoitomtipl jjlpom^tm 

ILLUSTRATED BY THE 

LUNATELLUS. 



ILLUSTRATION 1. 



MOTIONS OF THE SUN, EARTH, AND MOON, AND DIRECTION 
OF THEIR MOTIONS. 

By connecting the crank with the gearing, and turning it the 
proper direction, from left to right, motion is imparted to the Sun, 
earth and moon. The direction of the Sun's motion on his axis ; 
the Earth's annual motion around the Sun, and her daily motion on 
her axis ; and the motions of the Moon around the Sun, around 
the Earth, and also on her axis, are in the same general direction, 
Eastward. 

ILLUSTRATION 2. 

THE PLANE OF THE ECLIPTIC, AND ITS RELATION TO THE 
PLANE OF THE EQLATOR. 

Place the Indicator around the Earth, with one part touching the 
Tropic of Cancer, on top of the Earth, and another touching the 
Tropic of Capricorn, under the Earth, crossing the Equator on the 
east and west sides of the Earth, at an angle of about 23J°, and it 
will represent the plane of the Ecliptic in its proper relation to the 
plane of the Equator. 

ILLUSTRATION 3. 

INCLINATION OF THE EARTH'S AXIS, AND ITS PARALLELISM. 

Place the Indicator on the Earth so that it will represent the 
plane of the Ecliptic, and it may be readily perceived that the 



=§ 



===================== ===g( 

QEOGRAPHIGAX AM' A- 1K< >N< >M H A I. APPARATUS. 13 

Earth's axis is leaned about 23i c from an imaginary Hne passing 
through the centre of the Earth, perpendicular to the plane of the 
Ecliptic. Revolve the Earth once around the Sun, and the imagi- 
nary lines that represent the position of the Earth's axis at every 
point in her orbit are parallel to each other. 

ILLUSTRATION 4. 

CAUSE OF DAY AND NIGHT. 

The Earth being globular and opaque, the Sun always enlightens 
that half next himself, making clay, while the other half which is 
opposite to him is in darkness, makiug night. By giving the In- 
strument motion, the Earth turns on its axis, and that half which 
is in the Sun light is turned into the shade of the Earth, which is 
night, while the other half which is in darkness, is turned into Sun 
light, which is day. 

ILLUSTRATION 6. 
DAY AND NIGHT EQUAL, AND CAUSE. 

Give the Instrument motion till the Earth arrives at V. E., as 
marked on the Zodiac, indicating Vernal Equinox, or at A. E., 
indicating Autumnal Equinox, and it is apparent that each pole is 
equally distant from the Sun, and that the light of the Sun extends 
to each pole ; consequently half of the Equator is in the presence 
of the Sun, and half in darkness, and if the Earth is made to turn 
uniformly on her axis, as in nature, each half will pass through the 
same space in the same period, hence the equality of day and 
night. 

ILLUSTRATION 6. 

LONG DAY- AND SHORT NIGHTS IN THE NORTHERN 
HEMISPHERE. 

( Jive motion to the Instrument till the Earth arrives at the point 
in the Zodiac marked -S'. 81, indicating Summer Solstice. Apply 
the Indicator around the Earth to the circle of illumination, which 
is below the north pole 23^,°, and above the south pole the same 
number of degrees, and more than half of the Northern and less 
than half of the Southern Hemisphere is enlightened. Give the 
Earth, by turning the crank, a uniform motion on her axis, as in 



: 



14 GUIDE FOR USING DAVIS' 



nature, and the cause of the long days and short nights in the 
northern hemisphere, and short days and long nights in the south- 
ern hemisphere is apparent. 

ILLUSTRATION 7. 

LONG DAYS AND SHORT NIGHTS IN THE 
SOUTHERN HEMISPHERE. 

Give motion to the Instrument till the Earth arrives at that 
point of the Zodiac marked W. S. indicating Winter Solstice. 
Apply the Indicator around the Earth on the circle of illumination, 
which is below the north pole 23J degrees and above the south 
pole the same number of degrees, and more than half of the south- 
ern and less than half the northern hemisphere is enlightened. 
Give the Earth, by turning the crank, a uniform, motion on her 
axis, as in nature, and the cause of the short days and long nights 
in the northern hemisphere, and the long days and short nights in 
the southern hemisphere is apparent. 

ILLUSTRATION 8. 

SIX MONTHS DAY AT THE NORTH POLE, AND SIX MONTHS 
NIGHT AT THE SOUTH POLE, AND VICE VERSA. 

Bring the Earth to the Vernal Equinox and each pole will be 
equally distant from the Sun, and his light will extend to each 
pole. Turn the crank and apply the Indicator on the circle of il- 
lumination around the Earth, at any point in her orbit whilst 
she is making half of a revolution around the Sun, (equal half 
a year,) and it will pass outside the north pole from the Sun and 
inside of the south pole. The Sun being constantly above the In- 
dicator the north pole will enjoy his light, while the Earth is mak- 
ing half a revolution around the Sun, (equal to .six months,) and 
the south pole will be in darkness the same number of months. 
(When the earth is at the Summer Solstice the light of the Sun 
will extend below the north pole 23J degrees, and be withdrawn 
from the south pole the same number of degrees.) Continue the 
motion of the Earth in her orbit till she passes from the Autumnal . 
to the Vernal Equinox, (equal Jialf a year,) and consider the con- 
stant change of the circle of illumination, and it will be apparent 



GEOGKAPHh U. AND \-TKt fBOMH ' \ I . APPARATUS. 15 

that there will be day during all this time at the south pole and 
ni<jht at the north pole. (When the Earth is at the Winter Solstice 
the light of the Sun extends above the south pole '2o\ degrees and 
is withdrawn from the north pole the same number of degrees.) 

ILLUSTRATION 9. 

CAUSE OF THE INEQUALITY IX LENGTH OF DAYS 
AND NIGHTS. 

Were the Earth's axis perpendicular to the plane of the Ecliptic, 
the planes of the Equator and Ecliptic would coincide, and day and 
night would be always equal, as the light of the Sun would con- 
stantly extend to each pole, but the inclination and parallelism of 
the Earth's axis a?id her annual motion, as may be observed by giv- 
ing the earth a complete revolution around the sun, cause, more 
than halt' the northern hemisphere to be enlightened each alter- j 
Date halt' year, and more than half of the southern hemisphere to 
be enlightened each alternate half year, hence the inequality in 
the length of day- and nights in each hemisphere. 

ILLUSTBATION 10. 

I BANOE OF BBASONS, AND CAUSE. 

A- a rule the more dired the Sun's ray.- are on any portion of ; . 
the eajth, the warmer it is. Bring the earth to the Summer Solstice 
and the rays of the Sim will be direct on the Northern Tropic. 

e her bIo^i ly to the Winter Solstice and the Sun's rays t/nffoe ; 
direct on every parallel between the Tropics. Continue her in her 
orbit to th<' Summer Solstice and his rays will again be direct on 
every paralli 1 between the tropics, hence the change of se 
This change of place oft! ys is caused by the in- .: 

clination and parallelism of the earth's axis and her motion around \ 
tin - 

LLLUS1 B \TK>X 11. 

( A.USE OF Till: ZONES, AND THEIR WIDTH. 

Bring the Earth to the Summer Solstice and the Sun will be north ;j 
of the Equal ve her to the Winter So 

and he will rees south of the Equator. This change of j! 



16 GUIDE FOE USING DAVIS' 

the Sun from his extreme point north to his extreme point south is 
produced by the inclination of the Earth's axis and her annual rev- 
olution around the Sun. Double 23^ degrees, the amount of the 
inclination of the Earth's axis, and the sum will represent the width 
of the torrid zone. The distance of the polar circles from the poles 
is equal to 23 J degrees which equals the inclination of the Earth's 
axis. The temperate zones are limited by the tropics and polar 
circles. 

ILLUSTRATION 12. 

WINTER IN THE NORTHERN HEMISPHERE WHEN THE EARTH 

IS NEAREST, AND SUMMER WHEN THE EARTH IS 

FARTHEST FROM THE SUN. 

Bring the Earth to the Winter Solstice, as marked on the Zodiac, 
where she is nearest to the Sun, and his rays will be oblique to the 
northern hemisphere, hence winter there. Next bring the Earth 
to the Summer Solstice where she is farthest from the Sun, and his 
rays will be direct on the northern tropic, hence summer in the 
northern hemisphere. 

ILLUSTRATION 13. 

THE SUN RISING NORTH OF THE EAST POINT, AND SETTING 

NORTH OF THE WEST POINT, AND RISING SOUTH OF 

THE EAST POINT, AND SETTING SOUTH 

OF THE WEST POINT. 

Revolve the Earth around the Sun and it will be apparent that 
in consequence of the inclination of her axis, and her annual mo- 
tion, that the Sun will be, during each alternate half year, north 
and south of the Equator. While he is north of the Equator he 
will rise north of the east Point, and set north of the west Point, 
and while he is south of the equator he will rise south of the east 
Point, and set south of the west Point. 

ILLUSTRATION 14. 

CAUSE OF THE SUN RISING EARLIER TO PLACES EAST OF US. 

It will be remembered that East is a relative term, and in gene- 
ral, indicates the direction of the Sun's rising. To simplify this 
illustration bring the Earth to the Vernal Equinox, and apply the 



LAPHICAL AND ASTRONOMICAL APPARATUS. 



17 



Indicator around the Earth on thecircle of illumination which passe 
through the poles and divides the Equator into two equal parts. 
Revolve the Earth, and as she turns Eastward on her axis, those 
portions of her near the eastern line of illumination will be brought 
into the presence of the sun sooner than those parts further west. 



ILLUSTRATION 15. 

CAUSE OF THE APPARENT MOTION OF THE SUN, MOON AND 
STARS, FROM EA.ST TO WEST. 

By giving motion to the Instrument, the Earth may be seen 
turning Eastward on its axis, which causes the apparent westward 
motion of the Sun, Moon and Stars. 



ILLUSTRATION 16. 

DECLINATION OF THE SUN, OR HIS APPARENT MOTION NORTH 
AND SOUTH. 

Bring the Earth to the Winter Solstice, and the Sun's rays will be 
direct on the southern tropic, and as she is being revolved to the 
Summer Solstice, he will seem to move north till his rays are direct 
on the northern tropic. Continue the Earth's annual motion till 
she arrives again at the AVinter Solstice, and the Sun will appear to 
move south. This apparent motion of the Sun North and South is 
called declination, and is caused by the inclination^ the Earth's 
axis, its parallelism, and her annual motion. The Sun's declination 
is measured from the Equinoctial North and South. 



ILLUSTRATION L 



RELATIVE POSITION OF THE EARTH TO THE SUN AT ANY 
GIVEN PERIOD OF THE YEAR. 

Revolve the Earth around the Sun, and when the arm that carries 
the Earth is over each space of the Zodiac that represents each 
month of the year, she will sustain her proper position and rela- 
tion to the Sun, at every point in her orbit. 
2 



18 GUIDE FOB rSI>-G DAVIS'* 



ILLUSTEATION 18. 

THE SUN AND EARTH ALWAYS IN OPPOSITE SIGNS OF 
THE ZODIAC. 

The natural p ■::: - :" the Zodiac is outside of the orbit of the 

Earth, and the plane of the Ecliptic divides it into two equal parts, 

3 : being on each side, North and South. As the Earth enters one 

; sign, the Sun enters the sign opposite, as mar be seen by observing 

j how the Sun and Earth are related to the Zodiac when motion is 

\\ given to the Instrument. TVhen the Earth is at the Vernal Eoui- 

. by looking towards the San, along the arm that carries the 

i ..;, ha will appear at the Autumnal Equinox, and when the 

: Earth is at the Summer Solstice, he will appear at the Winter Sol- 

i! stice. 

ILLUSTEATION 19. 

ELLLPTICITY OF THE EARTH'S ORBIT. 

It may be observed by giving the Earth one complete revolution 
around the Sun, and measuring her distance from the Sun at the 
jj Solstices and Equinoxes, that the Earth gradually leaves the : 
II her passage from the Winter to the Summer Solstice, and tih 
|] gradually advances nearer to the Sun as she passes from the 
!; mer to the "Winter Solstice, hence the curve that she describes is an 
;; ellipse, and the Sun is in one of the foci. 

ILLUSTEATION 20. 

INEQUALITY OF SIDEREAL AND SOLAR DAYS, AND CAUSE— 366 
REVOLUTIONS OF THE EARTH ON HER AXIS NECES- 
SARY TO PRODUCE 365 DAYS. 

The length of the Siderial Day is the time that it requires the 

; ; Earth to rotate once on her axis, and the length of the solar dav is 

ime that elapses between two consecutive transits of the Sun 

I over any given meridian. To make this illustration plain, bring the 

Earth to the Summer Solstice, and bring any meridian direc;> i - 

'I der the Sun, and it will pass over the top of the Earth. If m 

; is given to the Instrument till the same meridian is brought round 

H on top of the Earth again, this rotation of the Earth reprt: 

Siderial Day j but the is not complete till the same me- 



GSOGBAPHICAJ AN.' ASTRONOMICAL APPARATUS. 19 

ridian is brought again directly between the Sun and Earth, conse- 
quently the solar day is l-365th longer than the siderial day, 
which is caused by the annual, in connection with the daily motion 
ol' the Earth ; hence 366 revolutions of the earth on its axis are 
sary to make 365 solar days. 

ILLUSTRATION 21. 

SPRING AND NEAP TIDES. 

the attraction of both Sun and Moon has a tendency to ele- 
vate the waters of the ocean, when both bodies are on the same 
side of the Earth, or on opposite sides, there is high or Spring Tide, 
hen they are at right angles there is a Neap Tide. To illus- 
he Spring Tide, turn the crank till the Moon is between the 
Earth, and the Sun, or on the opposite side of the Earth, from the 
Son . To illustrate the Neap Tide, continue the motion of the Moon 
about a quarter of a revolution around the Earth, to quadrature, 
and her iijiueixce on the waters will be at right angles to that of 
the Sun. 

ILLUSTRATION 22. 

THE EFFECT OF SOLAR AND LUNAR DECLINATION ON 
THE TIDES. 

- always near the plane of the Ecliptic, and as 
and South the same number of de- 
- from the Equator, and as the tendency of the waters is to 
(hat cause them to rise, it will be ap- 
t by revolving tbe Earth and Moon, and observing their de- 
clination, that thr tides are not always highest on the Equator, but 
of it, and sometimes South of it. 

ILLUSTRATION 23. 

-E OF CONSTANT AND PERIODIC WINDS, TRADE WINDS, 
MON£ 

: is air in motion, and the trade winds are winds at and in 

the vicinity of. the Equator, which seem to be constantly blowing I 
ite their apparent Westward motion, re- 
tinf on the Equator passes 

J| 



•$ r============z==z. -.::..:. -~::~::::::::::::::::::::::::::::::v:::"":™ 

20 GUIDE FOE USING DAVIS' 



through more space than any point on the Earth in the direction of 
either pole. At certain distances North and South from the Equa- 
tor the atmosphere keeps pace with the Earth as she revolves on 
her axis, but in the vicinity of the Equator it does not move so 
fast, hence its constant apparent Westward motion. 

Periodic Winds North and South. — The declination of the 
Sun North and South, which has been illustrated, has its influ- 
ence in producing the periodic winds that bloAv North and South. 
By giving motion to the Instrument, the Sun becomes more or 
less vertical on the Northern or Southern hemisphere. As he de- 
clines North, localities North are heated by his direct rays, and 
the air ascends, and the wind blows in and takes its place, and as 
he declines South, similar results occur. 

Land and sea breezes occur daily in consequence of the daily 
motion of the Earth on its axis. Islands, especially within the 
tropics, being exposed to the more direct rays of the Sun, heat 
quicker during the day than the waters that surround them, and 
the air ascends and the winds blow towards them to take its place, 
and during the night they cool quicker than the waters that sur- 
round them, and the winds blow from them. 

ILLUSTRATION 24. 

THE MOON ALWAYS PRESENTS THE SAME SIDE 
TO THE EARTH. 

Give motion to the Instrument, and follow the Moon with the 
eye while she is making one revolution around the Earth, and 
the same side will continue towards the Earth. This results from 
her slow axial motion. She turns once on her axis while she re- 
volves once around the Earth. 

ILLUSTRATION 25. 

LENGTH OF LUNAR DAYS AND NIGHTS. 

If watch is kept upon the Moon while she revolves once around 
the Earth, each hemisphere will be turned once to the Sun, and 
will be in alternate light and darkness, hence one lunar day and 
night is equal to about twenty-nine of our days. 



I] LND AS1 UPPABATUS. 21 



[LLUSTRATION 26. 

TION, QUADRATURE, OPPOSITION. AND PHASES 
OF THE MOON. 

. - Mood q the j! 

■.111 be in conjunction and at her change; ;j 

advance her a quarter of a revolution around the Earth, and she jj 

will be in quadrature and half full; continue her motion till the ji 

Earth is between her and the Sun, and sh - 

inn. ;i 

Note. — It' the Earth and Moon were at their relative dii 

mid not appear directly outside of the Earth, from jj 
the Sun, or directly between the Sun and Earth, only when at or ji 

!j 

ILLUSTRATION 27. 

ELLIPTICTTY OF THE MOON'S ORBIT, AND ITS RELATH N T I 
THE PLANE OF TOE ECLIPTIC. 

The Moon's orbit in relation to the Earth is elliptical, and it ji 

the Eclipti died nodes. The jj 

plane of the t an angle of about 5° with the ;j 

plane of the Ecliptic. To illustrate these phenomena with the In- ji 

strument, give it motion, and the Moon may be seen moving in an jj 

ellipse, alternately nearer and further from the Earth, and if the ji 

wire that carries the moon is properly adjusted, she will slightly | ; 

alternate North and South of the plai every rev- \\ 

olution - - around the Earth. 

ILLUSTRATION 28. 

RETROGR 

The M ion during 

each Lunation. Their Westward movement will be better un 

y examining the form and motion of the di-k that is at- 

the Outer end of the arm that car- jj 
Earth and Moon. Tl slightly inclined on the 

face, which causes (when motion is given to the Instrument) the 

• in an elliptical orbit, and a!~<> to cross the plane of jj 



22 GUIDE FOR USING DAVIS' 

the Ecliptic North and South. And as the wheel that carries the 
disk revolves slowly West, making but one revolution while the 
Earth revolves eighteen times and a fraction around the Sun, (equal 
eighteen years and a fraction), the inclination of the disk is 
always changing its position slowly in relation to the plane of the 
Ecliptic, which causes the Moon to cross the plane of the Ecliptic 
a degree and a fraction further "West every Lunation. 

ILLUSTRATION 29. 

SYNODICAL AND SIDERIAL REVOLUTIONS OF THE MOON. 

To make this illustration plain, bring the Earth to the Winter 
Solstice, and the Moon under the Earth, between the Earth and 
Sun. Revolve the Instrument till the Moon comes again directly 
under the Earth, and she will have made a siderial revolution. If 
the motion of the Earth and Moon is continued till the Moon 
comes between the Earth and Sun again, she will have made a 
synodical revolution. She makes the Siderial revolution in about 
27J days, and the Synodical in about 29J days. If the Earth had 
no annual motion, and the Moon to revolve, she would make her 
synodical and siderial revolutions in the same period. 

ILLUSTRATION 30. 
SOLAR AND LUNAR ECLIPSES. 

When the Moon passes beticeen us and the Sun, she hides his 
light from us, hence a solar eclipse ; and when the Earth comes 
bttween the Moon and Sun, her light is obscured, hence a lunar 
eclipse. To illustrate with the Instrument, give it motion, and ob- 
serve the course of the Moon, and she will at one time be between 
the Earth and Sun, hence a solar eclipse, and at another time she 
will be on the opposite side of the Earth from the Sun, hence 
a lunar eclipse. 

ILLUSTRATION 31. 

WHY SOLAR AND LUNAR ECLIPSES DO NOT OCCUR EVERY 
REVOLUTION OP THE MOON. 

From observing the course of the Moon around the Earth, it 
might be inferred that there is a solar and lunar eclipse every rev- 



GEOGRAPHICAL AND ASTRONOMICAL APPARATUS. 23 

• 

olution of the Moon, but if we consider the Earth and Moon to 
assume their proper relative distances from the Sun and each other, 
and that the orbit of the Moon crosses the plane of the orbit of 
the Earth at two points, and that these crossing points are slowly 
changing their places around the Earth, it becomes apparent that 
the Moon will be generally so far North or so far South of the 
Earth that her shadow will not obscure the light of the Sun — 
neither the Earth's shadow obscure her light. Eclipses can only 
occur when the moon and her nodes are at or near an imaginary 
line extending from the centre of the Sun through the centre of 
the Earth. 

ILLUSTRATION 32. 

ALTITUDE OF THE FULL MOON NORTH, AND NEW MOON 
SOUTH, IN WINTER. 

Give motion to the Instrument till the Earth arrives at the 
Winter Solstice, and the Moon in conjunction. The Sun will be 
his minimum altitude, being South of the Equator 23J°, 
and the Moon being always near the Ecliptic, she has a less alti- 
tude than at any other season when she is new. That the Moon 
may attain her greatest altitude when full, give her half a revolu- 
tion around the Karth to opposition, and her altitude will increase 
about 47"-, which increase will make it greater than at any other 
season when she is full. 



ILLUSTRATION 33. 

ALTITUDE OF THE FULL MOON SOUTH, AND NEW MOON 
NORTH, IN BUMMEB. 

Bring the Earth to the Summer Solstice and the Moon in con- 
junction where she changes, and as she is always near the Ecliptic 
it i- apparent that she has a greater altitude than at any other 
season when she is new. That the Moon may be at her minimum 
altitude when full, revolve her half around the Earth toopposition, 
and it is apparent that her altitude i- less when Bhe is full than at 
any other season. 



J 



24 GUIDE FOE USING DAVIS' 



ILLUSTRATION 34. 

THE MOON'S FIRST QUARTER LOW AND THIRD QUARTER 
HIGH AT THE AUTUMNAL EQUINOX, 

Give motion to the Instrument till the Earth arrives at the Au- 
tumnal Equinox and the Moon in conjunction. Turn the crank 
slowly and the Moon will be seen moving South from the Equa- 
tor diminishing in altitude and running low. During the second 
quarter she regains the altitude she lost during the first, and dur- 
ing the third she will be seen moving North from the Equator, 
increasing in altitude and running high. 

ILLUSTRATION 35. 

THE MOON'S FIRST QUARTER HIGH AND THIRD QUARTER 
LOW WHEN THE EARTH IS. AT THE VERNAL EQUINOX. 

Give motion to the Instrument till the Earth arrives at the 
Vernal Equinox and the Moon in conjunction. Turn the crank 
slowly and the Moon will be seen moving North from the Equa- 
tor increasing in altitude and running high. During the second 
quarter she loses the altitude she gained during the first, and 
during the third she will be seen moving South from the Equator 
diminishing in altitude and running low. 

ILLUSTRATION 36. 

THE MOON'S LIBRATIONS. 

. , The Librations of the Moon are of Latitude and Longitude ; of 
Latitude when she alternately exposes a little more of her North 
and South Polar Regions, and of Longitude when she alternately 
exposes a little more of her Eastern and Western Limbs. To il- 
lustrate the' principle, imagine ourselves on the Equator of the 
Earth and revolve the Earth and Moon, and observe the Moon as 
she passes North and South of the Equator. When she passes 
North shee xposes more of her South Polar Regions and when 
she passes Sotith she exposes more of her North Polar Regions. It 
is also apparent that as she revolves, a little more of the Eastern 
and Western Limbs of the Moon come alternately into view. 



lPHICAL an UICAL A.PPAKATU8. 



2--. 



ILLUSTRATION 37. 

ZENITH AND NADIR. 

Wherever we may be on the Earth's surface the Zenith is an 
nary point in the heavens directly over head, and the Nadir 

is an imaginary point in the opposite direction. Take any point on 
irth's surface, and consider ourselves located there, a straight 

line passing from the centre of the Earth through that point will 
• • the Zenith, and if it is extended in the opposite direction 

it will point to the Nadir. 

ILLUSTRATION 38. 

THE SENSIBLE AND RATIONAL HORIZON. 

If we imagine ourselves on any point of the Earth's surface and 
apply the Indicator around the Earth 90 degrees distant from us 
at all points it will represent the position of the plane of the Ra- 
tional Horizon. The Sensible Horizon is the circle where the 
Earth and the sky seem to come together. 

ILLUSTRATION 39. 
VERTICLE CIRCLES, PRIME VERTICLE AND COLURES- 

Verticle Circles are imaginary circles that pass through the Ze- 
nith and Nadir perpendicular to the horizon. Apply the Indica- 
tor around the Earth touching its surface at the point where we 
are on the earth, and also at the opposite point * on the op- 
posite side of the Earth and it will cut our horizon at right angles 
and represent the position of a Verticle Circle. If the Indicator 
is made to pass through the point we occupy, also through the East 
and "West points of our horizon, it will represent the position of 
the Prime Verticle. The Colures are great Meridian Circles that 
pass through the Equinoctial and Solstitial poin 

ILLUSTRATION 40. 

CIRCLES OF PERPETUAL APPARITION AND OCCULTATION. 

The Circle of Perpetual Apparition is the boundary of the space 
around the elevated pole where the Stars never set, and the Cir- 



o 



:« 



26 GUIDE FOR USING DAVIS' 



cle of Perpetual Occultation is the boundary of that space around 
the depressed pole where the Stars never rise. Were we on the 
Equator our horizon would pass through the poles and each half 
of the heavens would rise and set alternately as the Earth rotates 
on her axis. Were we to go North 40 degrees the North Pole 
would be apparently elevated 40 degrees, and the South Pole ap- i 
parently depressed the same number of degrees, and the space in i 
the heavens around the North Pole would have a radius of 40 de- j 
grees, in which the Stars would never set, and the space in the j 
heavens around the South Pole would have an equal radius in ; 
which the Stars would never rise. To illustrate the principle let ! 
us imagine ourselves- on the parallel 40 degrees North, keeping i 
constant watch, as the Earth is made to revolve, on some object 
towards which the North Pole is directed, and it will be apparent 
that the object will be constantly in view, and it will also be equally 
apparent that the interposition of the Earth will prevent us seeing 
other objects South of the South Pole. 



ILLUSTRATION 41. 

THE SUN'S ZENITH DISTANCE, ALTITUDE AND DECLINATION 
FOR LATITUDE 40 DEGREES NORTH OR SOUTH, WHEN THE 
EARTH IS AT THE YERNAL OR AUTUMNAL EQUINOX. 

The Sun's Zenith Distance is his distance from the Zenith meas- 
ured on a Verticle Circle. His Altitude is his distance from the 
horizon measured on a Verticle Circle, and his Declination is his 
distance North or South measured from the Equinoctial. To il- 
lustrate bring the Earth to the Vernal Equinox and the Sun will 
be on the Equator. Now if we imagine ourselves 40 degrees North 
or South of the Equator, at mid-day, and apply the Indicator 
around the Earth distant from us at all points 90 degrees, it will 
represent our horizon, and it will be apparent that the Sun has no 
declination as he is on the. Equator, that his Zenith distance is 40 
degrees, equal to our Latitude; and his altitude is 50 degrees, the 
compliment of his Zenith distance. 



GEOGRAPHICAL AM> a.-TUoxomii'AI, APPARATUS, 27 



ILLUSTRATION 42. 

THE SUN'S ZENITH DISTANCE, ALTITUDE AND DECLINATION 

FOR LATITUDE 40 DEGREES NORTH WHEN Till: 

EARTH IS AT THE SUMMER SOLSTICE. 

T'j illustrate bring the Earth to the Summer Solstice and the 
Sun will be on the Northern Tropic. Now if we imagine our- 
selves 40 degrees North of the Equator at mid-day and apply the 
Indicator around the Earth distant from as at all points 90 de- 
grees, it will represent the horizon and the Stin's Declination will 
be 23| degrees North, his Zenith distance is 16J degrees, and his 
Altitude is 73} degrees, the compliment of his Zenith distance. 

ILLUSTRATION 43. 

THE SUN'S ZENITH DISTANCE, ALTITUDE AND DECLINATION 

FOR LATITUDE 40 DEGREES NORTH WHEN THE 

EARTH IS AT THE WINTER SOLSTICE. 

Bring the Earth to the Winter Solstice and the Sun will be on 

the Southern Tropic. Now, if we imagine ourselves 40 degrees 
North of the Equator at mid-day, and apply the Indicator around 
the Earth distant from us at all points 90 degrees, it will represent 
our horizon, and the Sun's Declination is 23>> degrees South, his 
le is 2(]\ degrees, and his Zenith distance is 63§ degrees, 
the compliment of his Altitude. 

ILLUSTRATION 44 

A RIGHT, OBLIQUE, AND PARALLEL SPHERE. 

' In a Right Sphere the apparent daily revolutions of the heavenly 
bodies are in circles perpendicular to the horizon. In order that 
they may appear so, we must be at the Equator. Let us im- 
agine ourselves on the Equator, and apply the Indicator around 
the Earth 90° distant from us at all points, and it will pass 
through the poles and represent our horizon. Now, revolve the 
Earth, and consider the Equator and parallels extended into the 
heavens, and they will be perpendicular to our horizon, and prop- 
erly represent the course of the daily circles of a Right Sphere. 

Ax Oblique Sphere. — The circles of daily motion in an Ob- 
lique Sphere are Oblique to the horizon. To illustrate, let us con- 



28 GUIDE FOE USI>"G DAVIS' 

skier ourselves 40° North of the Equator, and apply the Indicator 
around the Earth 90° distant from us at all points, and it will 
represent our horizon. Now, it may be seen by observing the par- 
allels, and considering that they truly represent the course of the 
circles of daily motion, that they are Oblique to our horizon. 

A. Parallel Spheee. — The circles of daily motion of a Par- 
allel Sphere are parallel to the horizon. Let us imagine ourselves 
on either pole, and apply the Indicator around the Earth on the 
Equator, and it will represent the horizon. Now, as all the par- 
allels are parallel to the Equator, it is apparent that as they rep- 
resent the course of the daily circles, they are parallel to the hori- 
zon, which coincides with the Equator. 

ILLUSTRATION 45. 

THE AZBIUTH AND AMPLITUDE OF A HEAVENLY BODY, ON, 
OR ABOVE THE HORIZON. 

Azimuth is reckoned 90° on the horizon from the North or 
South point, and Amplitude is reckoned 90° on the horizon from 
the East or "West point. To illustrate, let us imagine ourselves 
40 North of the Equator, and apply the Indicator around 
the Earth 90° distant at all points, to represent our horizon. If 
the body is on the horizon "West of North, count the number of 
degrees from the Meridian that it is West, for its Azimuth. 
For its Amplitude, count the number of degrees that it is East 
of the "West point. When the body is above the hori- 
zon, consider a verticle circle to pass through it, and reckon the 
A--.hnv.th from the Meridian to where this circle cuts the horizon, 
and the Amplitude, from the West point to where this circle 
cuts the horizon. 



HICA] AND ASTRONOMICAL APPARATUS. 29 



ggg^ As »ia?iy more illustrations can be made with this Appara- 
tus that are not contained in this Guide, the Teacher of Geography 
and Astronomy, to male his work thorough, should have the Lu- 
natellus or Heliotcllus always present during each recitation, that 
every idea contained in the lesson, or suggested by it, may be illus- 
trated, if possible, to the eye. 



We do not deem it necessary to give reference to sections 
or paragraphs in the various Geographies and Astronomies now in 
use that contain the matter of the illustrations in this Guide, as 
they may be readily suggested by the Teacher, as the classes ad- 
vance. 






so 



GUIDE FOR USING DAVIS 




Fig. 2 — Heliotellus. 



KU'tUCAI. AND ASTRONOMICAL APPARATUS. 31 



j4eliotellus. 

(See Cut on orrosiiE Page.'i 

The Heliotellus, in material, construction and operation, 
is similar to the Lunatellus, and embraces the Sun, Earth and 
Moon, and the two inferior planets. It illustrates all 
that the Lnnatellus does, and in addition the phenomena 
of Mercury and Venus. 



MERCURY. 

ILLUSTRATION 1. 

YEARLY AND DAILY REVOLUTIONS OF MERCURY. 

In nature Mercury revolves once around the Sun in about 87 
race on his axis, in about 24 hours. In the In- 
strument, when in motion, he revolves around the sun with a ve- 
locity relative to the annual velocities of the Earth, and Venus, and 
tates on his axis with a velocity relative to the velocities 
which they have on their axes. 

ILLUSTRATION. 2. 

JBT'8 AXIS PERPENDICULAR TO THE PLANE OF HIS 
ORBIT— ALSO ITS PARALLELISM. 

Apply the Indicator around Mercury on his Equator, and it will 
represent the position of the planes of his Equator and Orbit as 
they coincide. Now, since these planes coincide, it is apparent 
that his axis is perpendicular to both, and by keeping watch on 
Mi r iry as he revolves around the Sun, his axis will be seen 
always parallel to itself. 

ILLUSTRATION 3. 
MERCURY'S DATS AND NIGHTS EQUAL. 

It is apparent that the poles of Mercury at every point in his 
orbit are equi-distant from the Sun, ami that his rays at all times 



jj 32 GUIDE ¥0R USING DAVIS' 

1 1 reach them. This being the ease, it follows that 180° of his Equa- 
II tor is constantly in the light of the Sun, and as he in nature ro- 
1 1 tates uniformly on his axis, his days and nights are always equal. 

ILLUSTRATION 4. 

NO CHANGE OF SEASONS ON MERCURY. 
1| 
f-j As a rule, the nearer overhead the Sun is, or the more direct his 

j | rays are, the more intense is his heat. As the planes of Mercury's 

j| Equator and Orbit coincide, his axis being perpendicular to both, 

I] the Sun's rays are constantly direct on his Equator, and grow 

II more and more oblique towards his poles; consequently the tem- 

| ! perature diminishes from his Equator to his poles, and is constant- 

\\ ly uniform on each parallel. 

ILLUSTRATION 5. 

|| INFERIOR AND SUPERIOR CONJUNCTIONS OF MERCURY. 

I| Give the Instrument motion till Mercury comes between the 

|| Earth and Sun, and he will be in inferior conjunction. Continue the 

|| motion of the Instrument till Mercury arrives on the opposite side 

l| of the Sun from the Earth, and he will be in superior conjunction. 

ILLUSTRATION 6. 
MERCURY'S STATIONARY POINTS. 
i| To illustrate, give motion to the Instrument till the arms that 
|j carry Mercury and the Earth are at right angles. If we observe 
1 1 Mercury when he and the Earth are made to revolve, he for a short 
I i time will not appear to move in his orbit, because his pathway at 
J! that point deviates but little from a straight line which would 
j | pass from the Earth through him into space. 

II 

ILLUSTRATION 7. 

WHY MERCURY IS NOT VISIBLE AT INFERIOR AND 
SUPERIOR CONJUNCTIONS. 

Bring Mereury to Inferior Conjunction and he cannot be seen 
!i as his dark side is towards the Earth. Neither can he be seen 



QEOGRAIMIH'AI. ANi< W&TRONOMICAL APPARATUS. 33 



when revolved to Superior Conjunction in consequence of the in- 
tensity of the Sun's light that intervenea between him aud the 
Earth. When be happens at his stationary points during the 
months of .March and April, August and September, ho may be 
seen in the twilight before Sunrise and after Sunset. 

ILLUSTRATION 8. 

PHASES OF MERCURY. 

Bring Mercury to Inferior Conjunction and he is invisible, as 
his dark side is towards the Earth. Continue the motion of 
the Instrument till Mercury is in quadrature, and like the Moon 
when she is in quadrature, half of his enlightened side will be 
towards the Earth. Next, bring Mercury to Superior Conjunc- 
tion and as he is on the opposite side of the Sun from the Earth 
the whole of the enlightened side will be towards the Earth; as he 
continues in his orbit he presents less and less of his enlightened 
surface till he comes again to Inferior Conjunction. 



VENUS. 
ILLUSTRATION 1. 

YEARLY AND DAILY REVOLUTIONS OF VENUS. 

In nature Venus revolves once around the Sun in about 225 
days, and rotate- once on her axis in a little less than 24 hours. 
In the Instrument, when put in motion, she revolves around the 
Sun with a velocity relative to the annual revolutions of Mercury 
and the Earth : and she also rotates on her axis with a velocity 
relative to the velocities which they have on their axes. 

ILLUSTRATION 2. 

INCLINATION OF THE AXIS OF VENUfr-ITfi PARALLELISM 
AM) THE PLANE OF HER ORBIT. 

Venus is pivoted bv her North Pole to the gea'ing. The axis 
3 



9 



lv 



34 GUIDE FOE USING DAVIS' 

of Venus is inclined 75 degrees to the plane of her orbit, causing 
her Tropics to be only 15 degrees from her Poles and her Polar 
Circles only 15 degrees from her Equator. Apply the Indicator 
around Venus, touching her Northern Tropic at the highest fjoint 
and her Southern Tropic at the lowest point to represent the plane 
of her orbit, and her axis will be at its proper inclination to it. Now 
as her axis has always the same inclination it is constantly parallel 
to itself. 

ILLUSTRATION 3. 

DECLINATION OF THE SUN ON VENUS. 

To illustrate the Sun's declination on Venus give motion to the 
Instrument till she arrives at the Summer Solstice, and he will be 
verticle to Venus 75 degrees North of her Equator, and if her mo- 
tion around the Sun is continued till she arrives at the Winter Sol- 
stice he will be verticle to Venus 75 degrees South of her Equa- 
tor. Now as Declination on Venus is measured from the Equinoc- 
tial of Venus North and South ; the maximum declination of the 
Sun on Venus is equal to the number of degrees that her axis is 
inclined to the plane of her orbit. 

ILLUSTRATION 4. 

EIGHT SEASONS ON VENUS AT HER EQUATOR AND 
FOUR AT HER POLES. 

To illustrate the seasons of Venus, give motion to the Instru- 
ment till she arrives at the Vernal Equinox, and the Sun will be 
on her Equator, hence midsummer there. Advance her in her 
orbit till she arrives at the Summer Solstice, hence midsummer at 
the Northern Tropic. Advance her next till she arrives at the 
Autumnal Equinox, and the Sun will be again on her Equator, 
hence midsummer again at her Equator. Next bring her to the 
Winter Solstice, hence midsummer at her Southern Tropic. It is 
now plain that as the Polar Regions of Venus are not tar North 
nor South of her Tropics, that they correspond to our Temperate 
Zones, hence four seasons in each during one of her years. And 



.K.vi'iikAl. AM' ABTBONOMICAX AJPPABATUB. 05 

the Sun crosses her Equator twice in one of her years, and 
declines 75 degrees North and 75 degrees South, she has two 
Summers at her Equator, and if she has two Summers there, she 
must have two Springs, and two Autumn--, and two AV inters. 

[LLUSTRATION 5. 

TONUS THE MORNING AND EVENING STAR 

To make this illustration plain revolve the Instrument till Ve- 
nus is above the Suu and the Earth at the Vernal Equinox, and 
the direction of the motion of the Earth on its axis shows that the 
the evening before Venus. To show her as the Morn- 
iiiir Star continue the motion of the Instrument till Venus is above 
the Sun and the Earth at the Autumnal Equinox, and the diree- 
: the motion of the Earth on its axis shows that Venus rises 
the Sun. 

ILLUSTRATION 6. 

SYNODIC PERIOD OF VENUS. 

It requires Venus about 225 days to revolve once around the 
Sun, which is her Siderial period. Her Synodic period is represent- 
ed by revolving Venus from Inferior Conjunction to Inferior Con- 
junction again. As the Earth and Venus revolve around the Sun 
in the same direction, the Synodic period of Venus is more than 
double the length of the Siderial period. It contains about 585 
day-, half of which time Venus is the Morning Star and the other 
half the Ev. 

[LLUSTRATION 7. 

PHASES OF VENUS. 

Brin Inferior Conjunction and she is invisible, as the 

Earth is "n the dark side of her. Revolve her till she is in quad- 
rature, and the half of the side that was turned from the Earth at 
conjunction i- now turned towards the Earth. Next revolve \ e- 



St: 



36 GUIDE FOR USING- DAVIS' 



nus to Superior Conjunction and her disk will be circular, as the 
■whole half that is enlightened is turned towards the Earth. 



ILLUSTRATION 8. 
TRANSITS OF MERCURY AND VENUS. 

Sometimes Mercury and Venus pass directly between the Earth 
and the Sun. When this happens each seems like a small black 
spot crossing his disk. To illustrate with the Istrument give it 
motion and observe Mercury and Venus pass between the Earth 
and the Sun. 

If Mercury, Venus and the Earth were at their relative distan- 
ces from the Sun they would seldom pass over his disk. 

ILLUSTRATION 9. 

OCCULTATION OF VENUS. 

The Occultation of a heavenly body takes place when another 
heavenly body passes between it and the Earth and conceals it 
from view. The Moon, at times, passes between the Earth and 
Venus and hides her from view. By giving motion to the Instru- 
ment you can readily perceive, from the arrangement and motions 
of the Earth, Moon and inferior Planets, how an Occultation of 
Venus may occur. 



B~ 



« 



QB0GRAPHICA1 am> .\> I i:o\omica I. AITAKATUS. 37 



pris' f tyurcttts 4 Irfww 



This work is designed mainly a> a Text-Book, and has been pre- 
pared with special reference to filling a vacuum in Academies, 
>ls, &c It differs from all others on the same subject in ar- 
rangement, simplicity, and adaptation to the youthful mind, and in 
addition illustrates, in a familiar manner, all the principal facta 
connected with the science of Astronomy. The engravings, of 
which over one hundred have been introduced, are striking and 
beautiful, and superior to those of any similar work. The Sun, 
and heavenly bodies with which wc are by observation most fa- 
miliar, arc first treated of; and step by step the student is ad- 
i to the investigation of worlds and systems revealed to us 
only by the telescope. The vocabulary of Astronomical terms 
and phrases, and the explanatory notes interspersed through the 
treatise, are valuable features of the work, and evidence the care 
i its arrangement. 

The latest discoveries and most reliable theories are presented, 
and will be introduced as made, thus furnishing at all times a 
hool Astronomy, in keeping with the scientific progress 
of the age. 

It has been prepared in a clear, distinct and handsome manner 
throughout, and the attractive style in which it is wrili n will 
commend it to every instructor of youth, as well as invite the pe- 
rusal of those who wish to freshen the studies of past years. All 
who have examined the work unite in pronouncing it Ote book long 
wanted. 

Published in 12mo form, cloth ; Do') pag 



.1 TAberai Discount will f>r Allowed for Virxi in'roduction. 






8 GUIDE FOR USIXG DAVIS' 



; From James M'C'lune,. Professor of Astronomy and Mathematics, 
Central High School, Philadelphia : 

" The Elements of Astronomy, by J. Davis, A. M., is a valua- 
I ble addition to the number of Text-Books on that subject. In 
I this work the leading facts and principles of the science are clearly 
! stated, properly arranged and well illustrated. Besides its val- 
I ue to the Instructor, it contains much which cannot fail to interest 
I and benefit the general reader. It is to be hoped that this and 
I every other effort to diffuse a knowledge of the oldest and nearest 
I perfect of the sciences, will be encouraged and sustained." 

The Heliotellus and Lunatellus show the movements of the 
I heavenly bodies with a clearness and accuracy which drawings and 
; descriptions fail to give. 

! From Rev. Francis AVolle, Principal and Superintendent of Young 
Ladies' Seminary, Bethlehem, Pa.: 

; * * * u l_t is just the book I found wanting during the past 
j thirty years of my experience in teaching. * * * The Author's 
I arrangement comes up to my ideal of a proper book upon the sub- 
I ject. I gave it a hearty welcome upon first acquaintance, and the 
! more I see of it and its workings in the School-room, the more I 
! admire." 



»= 



QBOG KAPUKWl. AND ASTRONOMICAL AlM'ARATl'S. o9 |: 



From Prof. F. W. Hastings, aud Faculty, of Mantua Institute, 
West Philadelphia: 

•• We have examined, with great interest and satisfaction, 

riot'. J. Davis' Elements of Astronomy, and are persuaded 
that it meets a demand long felt by Teaehers of Astronomy. We 
know of no other Elementary Work on this most ancient and inter- 
esting science bo well adapted to the purpose lor which it is de- 
signed. For conciseness and clearness of statement, it is without 
an equal among all the works on the science we have examined. 
His Xe\\ Astronomical Apparatus is without a rival, and is 
an invaluable aid to the learner, who wishes to have a clear con- 
ception ,»!' :,li, Astronomy of the Solar System." 



From George Woods, LL. D., President of the Western Univer- 
sity, Pittsburgh, Pa.: 

•• I have examined, with much pleasure, Mr. J. Davis' very 
ingenious Apparatus for illustrating the principles of Geography 
and Astronomy. It is so simple, and well contrived, that no pu- 
pil in these branches can fail to be interested in it, or to derive 
profit from it. Its general use in all our Schools, Seminaries and 
Colleges cannot fail to aid the student, and give life and interest 
to these important studi- s.* 

Prom Hon. Tho. II. Burrowes, Editor Penn'a. School Journal: 

" Elements of Astronomy, by -J. Davis, is the best 
Text-Book of Astronomy we have met with." 

From F. Thompson, Bishop M. E. Church, Delaware, O.: 

" The Elements of Astronomy, by J. Davis, Pittsburgh, is 
admirable for its style, arrangement and engravings, and may be 
heartilv commended as an introduction to the noble science of 
which it treat-. 



§5 



40 GUIDE FOR USING DAVIS' 



From Prof. G. W. Hough, Director of Dudley Observatory, Al- 
bany, New York : 

"I have examined, with great interest, Professor J. Davis' 
Apparatus for illustrating the various motions of the heav- 
enly bodies. He has succeeded admirably in presenting to the eye 
the movements of the planets and satellites of the solar system, 
showing at a glance the grand mechanism of the heavens. To 
the student of Astronomy this Apparatus cannot fail to be of very 
great service, in giving him just conceptions regarding the funda- 
mental principles of the science. I would therefore recommend 
its use in Schools, Colleges, and institutions of learning generally." 

From Prof. C. S. Lyman, Sheffield Scientific School of Yale Col- 
lege: 

"I concur fully in the above recommendation of Prof. J. Davis' 
Astronomical Apparatus, given by Prof. G. W. Hough." 

From Prof. J. C. Watson, Michigan University, Ann Arbor, 
Michigan : 

" I concur in the foregoing testimonial of Prof. G,¥. Hough, 
and recommend the Astronomical Apparatus to the favorable 
consideration of school officers in Michigan." 



From M. Simpson, Bishop of the M. E. Church, Philadelphia : 

"I have examined, with some care, a School Astronomy, by 
Prof. J. Davis, and believe it well adapted to purposes of instruc- 
tion. I have also seen his Apparatus, prepared to illustrate 
the motions of the heavenly bodies, and consider it a valuable 

aid to Schools and Seminaries." 



From the Very Eev. E. Puree] 1, V. G., Cincinnati, O.: 

* * * " Prof. J. Davis' Apparatus for illustrating Geogra- 
phy and Astronomy cannot fail to be of very great value in the 



GKOGRAlMIIi-VI. A.HD AS TKOXOMICAL APPARATUS. 41 



Family and School-room. * * * His Elements of Astronomy 
i-; an excellent Text-Book lor Schools. Academies and Seminaries." 



From Nathaniel B. Shurtleff, Mayor of Boston, and President of 
the School Committee, Boston : 

Having examined the Heliotellus and Lunatellus, invented by 
Prof. John Davis, for illustrating the most essential movements of 
the heavenly bodies, I have no hesitation in saying that they are 
admirably contrived for the purpose for which they were intended. 



From J. D. Philbrick, Superintendent of Public Schools, Boston: 

Having examined, with some care, Prof. Davis' Heliotellus and 
Lunatellus, it gives me pleasure to commend these ingenious in- 
struments for illustrating some of the most important phenomena 
of the planetary system. The latter is particularly valuable for 
showing very clearly the Geography of the Earth, and its relation 
to the Sun : while the former exhibits in a satisfactory manner 
some of the arrangements, relations and motions of the principal 
bodies composing the solar system. They are both well worthy 
the attention of teachers and school officers. 

From R. C. Waterson, Chairman Everett School Committee, 
Boston : 

I fully concur in the above statements of Mayor Shurtleff and 
Mr. John D. Philbrick, the Superintendent of Schools. 



From George J. Lnckey, Superintendent of Public Schools, Pitts- 
burgh : 

I have examined Prof. Davis' New Apparatus, and consider it 
the best that I have ever seen. By its use the smallest pupils in 
our Grammar Schools readily understand the motions of the heav- 
enly bodies. 



42 



GUIDE FOB USING DAVIS' 



His School Astronomy is written in a plain, comprehensive 
style, making it the most desirable Text-Book on that subject now 



From A. T. Douthett, County Superintendent Public Schools, Al- 
legheny County, Pa.: 

I have examined, with great care, Prof. Davis' Heliotellus and 
Lunatellus for illustrating Geography and Astronomy. They are 
without a rival, and cannot fail to be of invaluable service for 
School purposes. I would therefore most cordially recommend 
their introduction into every school in our county. 



=============== 

GEOGRAPHICAL LSD amkoxomhai. APPARATUS. 43 



jglA^ISPHEp, 



This Instrument is de- 
signed for the use of 
Schools, Academies, Sem- 
inaries and Families, and 
serves a similar purpose 
in determining the rela- 
tive position of the Stars 
and Constellations that 
Terrestrial Maps do in 
indicating the relative po- 
sitions of Countries and 
Localities on the Earth. 
It is composed of a 
permanent frame fifteen 
inches in diameter, and a movable horizon. The frame has im- 
printed on it in circular form, three hundred and sixty-five equal 
divisions, corresponding to each day in the year. Within this 
graduated circumference, all the prominent .Star.- that compose 
each Constellation to the distance of one hundred and forty degrees 
from the North Pole, are marked in relation to each other; and 
the Equinoctial and Ecliptic arc correctly drawn and properly 
graduated. 

The movable horizon, which answers to the natural one, turns 
en the point that designates the North Pole as its centre of motion, 
and it- circumference is divided into fourteen hundred and forty 
equal part-, corresponding to the number of minutes in each day. 



iff 
I A 


H.Wt 


nBUE 
HALL 

H 


L J, DA\ 


k 1 







44 GUIDE >OR USING DAVIS' 

The inner part of this movable horizon is elliptical, and has mark- 
ed on it the letters that indicate the various points of the compass. 
Across this horizon is a meridian scale, which is divided into one 
hundred and eighty degrees, and the point in it that rests on the 
point representing the North Pole is forty degrees from the horizon. 

Each Instrument is accompanied with a sufficient number of 
Examples and Rules, to explain its proper use. 

For sale by nil Booksellers and Agents who sell Davis' Appa- 
ratus and Elements of Astronomy. 



From B. Pierce, L. L. I)., Prof, of Astronomy and Mathematics, 
Harvard University, Cambridge, Mass. 

I have examined Prof. H. Whitall's Planisphere, and 
it seems to me to be a simple and economical substitute for a Ce- 
lestial Globe, and capable of being used for all the ordinary pur- 
poses to which globes are applied, and is especially to be recom- 
mended 'for the simplicity with which it presents to the eye some 
of the popular problems of Astronomy, and for the readiness with 
which it will enable one to ascertain the names and positions of 
the Stars. 

We fully concur in the recommendation of Prof. Pieroe. 

Hon. Gideon Wells, Secretary of the Navy. 

C. H. Davis, Rear Admiral and Chief of Bureau of Navigation. 

A. D. Bache, Supt. of U. S. Coast Survey. 

Joseph Henry, Secy. Smithsonian Institute. 

J. G. Barnard, Brig. Genl. and Lt. Col. of Engineers. 

J. Saxon, Asst. Supt Weights and Measures. 

L. M. Goldsborough, Rear Admiral U. S. Navy. 



&~. 



QEOOn.VrilirAl. \M> ASTRONOMICAL APPARATUS. 



4r, 



J. E. Hillgard, U. B. Coast Survey Office. 

Father -las. Curley, Proi* Astronomy and Mathematics George- 
town College, D. C. 

K. 1». Metcalf, Principal ofWayland School, Worcester, Mass. 

John D. Philbrick, Supt. Public Schools, Boston. 

Daniel Leaca, Supt. Public Schools, Providence. 

Alpheus Crosby, A. M. f Principal Suite Normal School, Salem, 
Mass. 

Henry Riddle, Asst. Supt. Common Schools N. Y. City. 

Rev. II. Mattison, Author of High School Astronomy, &c. 

S. S. Randall, City Supt. Public Schools, X. Y. City. 

William Bmaton, Principal Grammar School, No. 19, N. Y. City. 

J. F. Stoddard, Principal of Grammar School, No. 10, N. Y. City. 

Thomas Foulke, Principal Friends' Seminary, N. Y. City. 

Thomas Hunter, Principal, No. 35, Fifteenth Ward, N. Y. City. 

Thomas F. Harrison, Principal, No. 41, Ninth AVard, N.Y. City. 

Henry M. Park hurst, N. Y. City. 

C. Van Norman, No. 5 West Thirty-Fifth St., N. Y. City. 



46 



GUIDE FOR USING DAVIS 




Fij, l-Pl.-.iiit-He;. 



.lll< AI. AND ASTRONOMICAL APPARATUS. 47 



pJLANETELLE^. 



fter the lapse of nearly thirty years, lias finally crown- 
ed the efforts of the inventor of the Lunatellns and Heliotellus, in 
contriving the Pl \xi:ti:i.i.i:s. the first Mechanical device ever made 
that represents the motion of the Sun on his axis, the relative year- 
ly and daily motion- of the eight primary Planets, and the various 
motions of the fwenty-onc Satellites around the Sun, around their 
Primaries and on their axes in different periods. Eighty (80) mo- 
tions of these bodies, faithfully representing the grand Mechanism 
of die Solar System, with the Phenomena resulting therefrom, are 
clearly exhibited to the eye, by this invaluable Instrnmetn — this 
Mechanical Wonder. 

The Model of this improvement has been deposited, piecemeal, 
in the United States Patent Office, at Washington City, and an- 
other Instrument of large dimensions, of the same kind, is now 
I for Public use. 



LIBRARY OF CONGRESS 

003 538 883 7 # 



